The Increase in Earth’s Oxygen was Gradual

September 14, 2018

A recent study supports the idea that the Oxygen levels of Earth rose in a stepwise fashion.

The existence of gaseous Oxygen is one of the most vital factors, which allow colonization of the Earth. Its importance can be judged by the fact that astronomers looking for signs of life in different parts of the universe look for the presence of Oxygen on all possible candidates. According to a study published by the journal ‘Science’ on 22nd of March, the Great Oxidation Event (GOE) responsible for rise in Oxygen levels, which occurred nearly 2.3 billion years ago, is much more significant than previous conclusions. Clara Blättler, the First Author of the study who is a Postdoctoral Research Fellow in the Department of Geosciences at the Princeton University, said,

“Instead of a trickle, it was more like a firehose. It was a major change in the production of oxygen.”

Now, another massive development took place in this domain as a team of researchers, under the leadership of Dr. Huan Cui of the NASA Astrobiology Institute, found a Carbon Cycle Anomaly in the carbonate rocks of the Neoproterozoic Hüttenberg Formation. These rocks, located in the North-eastern parts of Namibia, follows a pattern similar to that found right after the Great Oxidation Event. Researchers at the University of Wisconsin-Madison studied the time during which the Earth transformed from a hostile place into a suitable environment for the animal kingdom to flourish.

The examination of the Hüttenberg Formation showed sustained, high levels of Carbon. These changes in the quantities of different elements, including Carbon, indicate that the variations in Oceanic Oxygen might have played an instrumental role in the early evolution of animals on our planet. The researching team gathered isotopic data for Oxygen, Strontium, and Sulfur and merged it with the Carbon isotope data collected in 2009. This combination of data strengthened the idea that the increment of atmospheric Oxygen was a gradual process. Simultaneously, it discouraged the theory that two major events, during the Proterozoic period, produced all the Oxygen we have in our environment. Dr. Alan J. Kaufman, the Lead Author of the 2009 Carbon isotope study and the Second Author of this study, referred to the importance of paired data by saying,

“It suggests that the rise of oxygen was oscillatory through this 50- to 75-million year interval associated with the Hüttenberg Anomaly and the Neoproterozoic Oxidation Event or NOE at the end of the Proterozoic.”

The anomaly showed that the ratios of carbon isotopes increased continuously for 15 million years at the rate of 12 to 14 parts per thousand before returning back to lower levels. The increase in the Oxygen levels of the ocean turned sulfides into sulfates. Some of the microbes used these sulfates for their metabolism and recycled organic Carbon on the seafloor. The cyclic fluctuations in the concentration of isotopes of Oxygen, Sulfur, and Carbon forced the scientists to believe that there is more to this story than a co-incidence.

Contrary to that, some wild fluctuations in the global Oxygen and Carbon cycle were also observed during the Proterozoic period. Researchers believe that these ancient Oxygen swings were critical for the evolution of multi-cellular life. More and more Oxygen in the water offered an opportunity to life to develop. Kaufman compared this jump of Oxygen with Lomagundi event. It is often referred as a ‘false start’ because the levels of Oxygen rose to a life-supporting state during this phase before they dropped again. He proposes that it is not possible for Oxygen to attain modern-day levels before the NOE in the following words:

“Here’s an isotope anomaly in the Neoproterozoic that is associated broadly in time with the NOE, but which has a rise and fall structure that looks very similar to the GOE. At both ends of the Proterozoic Eon there was continental rifting, glaciations, and profound carbon fluctuations; just as the GOE was likely responsible for the evolution of simple eukaryotes, the NOE was involved in the evolution of multicellularity.”

This study is being acknowledged by a lot of experts of the field. Dr. Paul Myrow, a Professor of Geology at the Colorado College who was not a part of the research, mentioned that the time constraints in this study will urge other researchers to re-examine ancient rock formations to see whether there are any other proofs of this anomaly.

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